Acidic aqueous composition for semiglossy tin plating and member having semiglossy tin plating film

ABSTRACT

An acidic aqueous composition for semiglossy tin electroplating has a water-soluble tin (II)-containing substance and a surfactant. The surfactant includes a surfactant (A) comprising N,N′,N′-polyoxyethylene-N-alkyl-1,3-diaminopropane. The surfactant (A) the number of carbon atoms of the alkyl group that bonds to N ranges from 14 to 18. The weight-average molecular weight of the surfactant (A) ranges from 300 to 1500.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an acidic aqueous composition for tinelectroplating.

In the present disclosure, the term “tin plating” denotes electroplatingwhich can form a film consisting of tin and impurities.

2. Description of the Related Art

Tin plating films are widely used in contact sections and solderconnections in electric and electronic components such as semiconductorchip components, crystal oscillators, capacitors, connector pins, leadframes, printed circuit boards and the like. Tin plating films includefilms having gloss, films lacking gloss, and semiglossy films that liein between. In the present disclosure, the term “semigloss” denotesglossiness G_(s)(60°) ranging from 10 to less than 200 (specifically, asmeasured using a measurement device IG-331 by Horiba Ltd., likewisehereafter), at an incidence angle of 60°, according to JIS 28741: 1997(ISO 2813: 1994). In the present disclosure, a glossiness G_(s)(60°)ranging from 20 to less than 150 corresponds to instances of goodsemi-gloss, and a glossiness G_(s)(60°) ranging from 30 to less than 100corresponds to instances of particularly good semi-gloss.

Patent Document 1 discloses a tin or tin-alloy electroplating solutionthat contains (1) a reaction product obtained by reacting glutaraldehydeand at least one compound selected from hydrocarbon compounds containinga hydroxyl group, in the presence of an acid, and (2) at least onecompound selected from amine compounds, and describes an example whereina tin plating film obtained through electroplating for 90 minutes at 0.1A/dm², using such a plating solution (liquid temperature: 20° C.), has asemiglossy appearance.

Patent Document 2 discloses a tin plating solution that contains astannous salt, a compound such as gluconic acid or the like, and asurfactant, and describes an example wherein a tin plating film obtainedthrough electroplating for 5 minutes to 20 minutes at 1 A/dm² to 4A/dm², using such a plating solution (liquid temperature: 30° C. to 55°C.), has a semiglossy appearance.

-   Patent Document 1: Japanese Patent Application Publication No.    2008-266757A-   Patent Document 2: Japanese Patent Application Publication No.    S57-63689A

SUMMARY OF THE INVENTION

One or more embodiments of the present invention provides an acidicaqueous composition for semiglossy tin plating that allows forming, withexcellent productivity, a semiglossy tin plating film of stable quality.

One or more embodiments of the present invention provides a member thathas a semiglossy tin plating film formed out of the abovementionedacidic aqueous composition for semiglossy tin plating.

Embodiments of the present invention include the following.

(1) An acidic aqueous composition for semiglossy tin electroplating,which contains a water-soluble tin (II)-containing substance and asurfactant,

wherein said surfactant includes a surfactant (A) comprisingN,N′,N′-polyoxyethylene-N-alkyl-1,3-diaminopropane.

(2) The acidic aqueous composition for semiglossy tin electroplatingaccording to (1), wherein in the surfactant (A) the number of carbonatoms of the alkyl group that bonds to N ranges from 14 to 18.

(3) The acidic aqueous composition for semiglossy tin electroplatingaccording to (1), wherein the weight-average molecular weight of thesurfactant (A) ranges from 300 to 1500.

(4) The acidic aqueous composition for semiglossy tin electroplatingaccording to (1), wherein the content of the water-soluble tin(II)-containing substance in tin content equivalent ranges from 5 g/L to200 g/L and the content of the surfactant (A) ranges from 0.5 g/L to 40g/L.

(5) The acidic aqueous composition for semiglossy tin electroplatingaccording to (1), further containing an organic sulfonic acid compound.

(6) The acidic aqueous composition for semiglossy tin electroplatingaccording to (5), wherein the content of the organic sulfonic acidcompound in organic sulfonic acid content equivalent ranges from 50 g/Lto 300 g/L.

(7) A member, comprising: a member to be plated; and a semiglossy tinplating film that is formed on at least part of the surface of themember to be plated, by electroplating of the acidic aqueous compositionfor semiglossy tin electroplating according to any one of (1) to (6).

(8) The member according to (7), wherein the semiglossy tin plating filmin the member is electroplated under a condition of current density of 5A/dm² or higher.

(9) The member according to (7), wherein the semiglossy tin plating filmof the member has a ratio of 8 or less of glossiness G_(s)(60°) measuredin accordance with JIS 28741: 1997 (ISO 2813: 1994) of the semiglossytin plating film obtained in a case of electroplating under conditionsof plating temperature of 45° C. and current density of 15 A/dm², withrespect to the glossiness G_(s)(60°) of the semiglossy tin plating filmobtained in a case of electroplating under conditions of platingtemperature of 45° C. and current density of 5 A/dm².

(10) The member according to (7), wherein the semiglossy tin platingfilm in the plating member has a ratio of 1.3 or less of arithmeticalmean roughness Ra measured according to JIS B0601:2001 (ISO 4287:1997)of the semiglossy tin plating film obtained in a case of electroplatingunder conditions of plating temperature of 45° C. and current density of15 A/dm², with respect to the arithmetical mean roughness Ra of thesemiglossy tin plating film obtained in a case of electroplating underconditions of plating temperature of 45° C. and current density of 5A/dm².

(11) The member according to (7), wherein the semiglossy tin platingfilm in the plating member has a ratio of 1.5 or less of root meansquare roughness Rq measured according to JIS B0601:2001 (ISO 4287:1997)of the semiglossy tin plating film obtained in a case of electroplatingunder conditions of plating temperature of 45° C. and current density of15 A/dm², with respect to the root mean square roughness Rq of thesemiglossy tin plating film obtained in a case of electroplating underconditions of plating temperature of 45° C. and current density of 5A/dm².

(12) The member according to (7), wherein the semiglossy tin platingfilm in the member has a thickness ranging from 1 μm to 5 μm.

(13) The member according to (7), wherein the semiglossy tin platingfilm in the member is formed by electroplating with a current densityranging from 5 A/dm² to 15 A/dm², and a ratio (before/after) of a valueof zero crossing time (unit: seconds) of the member as measured in asolderability test by a balance method according to JIS C60068-2-54:2009 (IEC60068-2-54: 2006) after an environment test of standing for 8hours in an environment at 105° C. and relative humidity of 100%, withrespect to the value measured before the environment test, is 2.1 orless.

(14) The member according to (7), wherein the member to be plated is anelectronic component.

(15) The member according to (14), wherein the electronic componentincludes one or more selected from the group consisting of resistors,variable resistors, capacitors, filters, inductors, thermistors, crystaloscillators, switches, connectors, lead wires, printed circuit boards,and semiconductor integrated circuits and modules.

The acidic aqueous composition for semiglossy tin plating according toone or more of the above-described embodiments allows forming asemiglossy tin plating film of stable quality with excellentproductivity. The member having a semiglossy tin plating film formedusing such an acidic aqueous composition for semiglossy tin platingexhibits excellent homogeneity in surface properties such as semiglossyappearance, solder wettability and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating plating deposition states of tinplating films obtained by electroplating at dissimilar currentdensities, using a plating solution 1 obtained in an example;

FIG. 2 is a diagram illustrating a plating deposition state of a tinplating film obtained by electroplating at dissimilar current densities,using a plating solution 2 obtained in an example;

FIG. 3 is a diagram illustrating a plating deposition state of a tinplating film obtained by electroplating at dissimilar current densities,using a plating solution 3 obtained in an example;

FIG. 4 is a diagram illustrating a plating deposition state of a tinplating film obtained by electroplating at dissimilar current densities,using a plating solution 4 obtained in an example;

FIG. 5 is a diagram illustrating a plating deposition state of a tinplating film obtained by electroplating at dissimilar current densities,using a plating solution 5 obtained in an example;

FIG. 6 is a diagram illustrating a plating deposition state of a tinplating film obtained by electroplating at dissimilar current densities,using a plating solution 6 obtained in an example;

FIG. 7 is a diagram illustrating a plating deposition state of a tinplating film obtained by electroplating at dissimilar current densities,using a plating solution 7 obtained in an example; and

FIG. 8 is a diagram illustrating a plating deposition state of a tinplating film obtained by electroplating at dissimilar current densities,using a plating solution 8 obtained in an example.

DETAILED DESCRIPTION

In embodiments of the invention, numerous specific details are set forthin order to provide a more thorough understanding of the invention.However, it will be apparent to one of ordinary skill in the art thatthe invention may be practiced without these specific details. In otherinstances, well-known features have not been described in detail toavoid obscuring the invention.

1. Acidic Aqueous Composition for Tin Plating

One or more embodiments of the present invention provides an acidicaqueous composition for semiglossy tin electroplating that contains awater-soluble tin (II)-containing substance and a surfactant, whereinthe surfactant containsN,N′,N′-polyoxyethylene-N-alkyl-1,3-diaminopropane. A tin plating filmhaving a semiglossy appearance can be obtained, even under conditions ofcurrent density of 5 A/dm² or higher, when using such a composition.Therefore, the plating rate can be increased, and productivity enhanced,as compared with instances of semiglossy tin plating according toconventional techniques. When such a composition is used, surfacecharacteristics such as appearance of the tin plating film, solderwettability and so forth do not readily fluctuate for a current densitylying within a wide range, from 5 A/dm² to 15 A/dm². Therefore, theobtained tin plating film has excellent homogeneity in surfaceproperties, even in cases where current density is likely to exhibitvariability, for instance in cases of barrel plating, or when thesurface that is to be plated in the member to be plated is a ruggedsurface.

(1) Water-Soluble Tin (II)-Containing Substance

The acidic aqueous composition for tin plating according to one or moreembodiments of the present invention (hereafter also referred to as“plating solution”) contains a water-soluble tin (II)-containingsubstance. The “water-soluble tin (II)-containing substance” denotes asubstance that comprises one, two or more substances selected from thegroup consisting of divalent tin cations (Sn²⁺) and water-solublesubstances that contain divalent tin cations.

Examples of starting-material substances (also referred to as “tin (II)sources”) that provide a water-soluble tin (II)-containing substance toa plating solution include inorganic stannous acid salts such asstannous sulfate, stannous chloride, and stannous fluoroborate; stannousalkanol sulfonates such as stannous isethionate; stannous alkanesulfonates such as stannous methanesulfonate and stannousethanesulfonate; aromatic stannous sulfonates such as stannousphenolsulfonate and stannous cresolsulfonate; and stannous carboxylatessuch as stannous citrate and stannous acetate. The foregoing may be usedsingly or in combinations of a plurality of types.

According to one or more embodiments of the present invention, thecontent of the water-soluble tin (II)-containing substance in tincontent equivalent in the plating solution ranges from 5 g/L to 200 g/L,and according to one or more embodiments of the present invention,ranges from 30 g/L to 100 g/L. If the content of the water-soluble tin(II)-containing substance is excessively low, tin plating may not bedeposited. On the other hand, if the content of the water-soluble tin(II)-containing substance is excessively high, the plating throwingpower may drop on account of the increased viscosity of the platingsolution. If the blending amount of the tin (II) source is excessivelyhigh, the plating solution comprises then both the water-soluble tin(II)-containing substance, in a dissolved state in the plating solution,and the tin (II) source in a solid state in the plating solution. Inthat case, the content of water-soluble tin (II)-containing substance inthe plating solution depends on the solubility of the tin (II) source.

(2) Surfactant

The plating solution according to one or more embodiments of the presentinvention contains a surfactant. The surfactant comprises anN,N′,N′-polyoxyethylene-N-alkyl-1,3-diaminopropane. In the presentdisclosure, this surfactant is referred to as “surfactant (A)”.According to one or more embodiments of the present invention, the alkylgroup that bonds to N in the surfactant (A) has 14 carbon atoms to 18carbon atoms.

According to one or more embodiments of the present invention, theweight-average molecular weight of the surfactant (A) ranges from 300 to1500, and according to one or more embodiments of the present invention,ranges from 500 to 1300, and according to one or more embodiments of thepresent invention, ranges from 900 to 1000, in terms of preventing thecloud point of the surfactant (A) from dropping down to the platingtemperature range and in terms of using a surfactant (A) that has gooddefoamability. According to one or more embodiments of the presentinvention, the number of consecutive oxyethylene groups in thepolyoxyethylene moiety of the surfactant (A) is 3 or more, from theviewpoint of stably bringing out the functionality of the surfactant,and according to one or more embodiments of the present invention, is 30or less, from the viewpoint of using a surfactant (A) that has gooddefoamability.

Through the use of the surfactant (A), the plating solution according toone or more embodiments of the present invention allows obtaining asemiglossy tin plating film having the below-described superiorcharacteristics. From the viewpoint of stably eliciting such an effect,according to one or more embodiments of the present invention, thecontent of the surfactant (A) ranges from 0.5 g/L to 40 g/L, andaccording to one or more embodiments of the present invention, from 1g/L to 20 g/L and according to one or more embodiments of the presentinvention, from 2 g/L to 10 g/L.

The plating solution according to one or more embodiments of the presentinvention may contain surfactants other than the surfactant (A). Interms of obtaining more stably the abovementioned semiglossy tin platingfilm having excellent characteristics, however, according to one or moreembodiments of the present invention, the plating solution contains noother surfactant. If other surfactants are used, according to one ormore embodiments of the present invention, the total content thereof issmaller than the content of the surfactant (A), and according to one ormore embodiments of the present invention, ¼ or less of the content ofthe surfactant (A), and according to one or more embodiments of thepresent invention, 1/10 or less of the content of the surfactant (A).

(3) Electrolyte Component

In addition to the abovementioned components, the plating solutionaccording to one or more embodiments of the present invention contains acomponent (hereafter also referred to as “electrolyte component”) forincreasing the electroconductivity of the plating solution. The type ofthe electrolyte component is not particularly limited. Examples thereofinclude acids inorganic acids such as sulfuric acid, hydrochloric acid,boric acid, and fluoroboric acid; organic sulfonic acids such as alkanolsulfonic acids, e.g., isethionic acid, alkane sulfonic acids, e.g.,methanesulfonic acid, and aromatic sulfonic acids, e.g., phenolsulfonicacid; and carboxylic acids such as acetic acid, citric acid, malic acid,tartaric acid or the like, as well as ammonium salts, sodium salts,potassium salts or the like of the foregoing acids. The above acids andsalts may be used singly or in combinations of a plurality to typesthereof. According to one or more embodiments of the present invention,among the foregoing are organic sulfonic acids and/or salts of organicsulfonic acids.

The content of the electrolyte component is not limited, but is to beappropriately set on the basis of, for instance, the current densityduring plating. In an example of the content range, the free-acidequivalent content ranges from 50 g/L to 300 g/L.

(4) Other Components

The plating solution according to one or more embodiments of the presentinvention may contain, for instance, a known brightening agent,brightening auxiliary agent, antioxidant, defoaming agent and the like.In a case where the plating solution contains a brightening agent and abrightening auxiliary agent, the content of the foregoing componentsshould remain within a range such that the appearance of the tin platingfilm obtained from the plating solution according to one or moreembodiments of the present invention is not glossy but remainssemiglossy. The brightening agent and the brightening auxiliary agentdecompose and/or polymerize on account of the acid contained in theplating solution, and/or due to electrolysis for electroplating. As aresult, the content of the above-mentioned components decreases as thetotal time of the plating process increases. Moreover, byproducts ofsuch decomposition and/or polymerization accumulate in the platingsolution, and, as a result, the stability of the plating solutiondecreases, and plating defects are brought about through adhesion ofsuch byproducts to the member to be plated. According to one or moreembodiments of the present invention, therefore, the plating solutioncontains substantially no brightening agent or brightening auxiliaryagent.

An antioxidant that the plating solution according to one or moreembodiments of the present invention may contain, as the case mayrequire, is an antioxidant for suppressing oxidation of tin (II) ions inthe plating solution according to one or more embodiments of the presentinvention. Examples of such antioxidants include catechol, hydroquinoneand the like. The content of the antioxidant is not limited, but in anexample, ranges from 0.05 g/L to 20 g/L, and according to one or moreembodiments of the present invention, from 0.1 g/L to 15 g/L. Examplesof the defoaming agent include organic defoaming agent such aspolyoxyethylene-polyoxypropylene block polymers, higher aliphaticalcohols, acetylene alcohols, polyalkoxylates and the like, as well assilicone-based defoaming agents.

(5) Solvent and pH

The solvent of the plating solution according to one or more embodimentsof the present invention has water as a main component. Examples ofsolvents other than water that may be mixed in include organic solventshaving high solubility in water such as alcohols, ethers, and ketones.In such a case, the ratio of the organic solvent, according to one ormore embodiments of the present invention, is no greater than 10 vol %with respect to the entire solvent, from the viewpoint of high stabilityof the entire plating solution and of easing the waste treatment load.

The plating solution according to one or more embodiments of the presentinvention is acidic. In a form according to one or more embodiments ofthe present invention, the solution is strongly acidic, and the pHthereof is ordinarily 1 or less. When incorporating the above-describedelectrolyte component, the plating solution can be set to a desired pHthrough adjustment of the amount of acid that is added.

2. Plating Condition

The plating conditions of the plating solution are not particularlylimited. Instances of the various conditions are set out below.

(1) Current Density

The current density of the plating solution according to one or moreembodiments of the present invention can be set to 5 A/dm² or higher.Plating abnormal deposition occurs, and glossiness decreasesdramatically in affected portions, when the current density is set to 5A/dm² or higher in conventional semiglossy tin plating solutions. In theplating solution according to one or more embodiments of the presentinvention, by contrast, the appearance of the obtained plating film canbe rendered semiglossy even if the current density is set to 5 A/dm² orhigher, and there can be obtained a tin plating film having aparticularly good semiglossy appearance (glossiness) G_(s)(60°) smallerthan 100) even with a current density of 15 A/dm². That is, the platingsolution according to one or more embodiments of the present inventionallows increasing current density beyond that in conventional platingsolutions, and allows increasing, in proportion, the deposition rate ofthe plating film. Therefore, the plating solution according to one ormore embodiments of the present invention allows enhancing theproductivity of plating film formation beyond that of a conventionalplating solution.

In a specific example, there can be achieved a ratio of or less for theratio of glossiness G_(s)(60°), measured in accordance with JIS 28741:1997 (ISO 2813: 1994), of the semiglossy tin plating film obtained usingthe plating solution according to one or more embodiments of the presentinvention in a case of electroplating under conditions of platingtemperature of 45° C. and current density of 15 A/dm², with respect tothe ratio of the glossiness G_(s)(60°) in a semiglossy tin plating filmobtained in a case of electroplating under conditions of platingtemperature of 45° C. and current density of 5 A/dm². In a case where anamine-based surfactant, for instance polyoxyethylene polyoxypropylenetallow amine is used instead of the surfactant (A) contained in theplating solution according to one or more embodiments of the presentinvention, a plating film can be obtained that has semiglossiyappearance (glossiness G_(s)(60°) equal to or greater than 150) close tothe gloss of a glossy film, at a low current density (5 A/dm²), while ata high current density (15 A/dm²) there is obtained plating film havingmatte appearance. A plating film having good semiglossy appearancecannot thus be obtained for a wide current density range of 5 A/dm² to15 A/dm², as is the case in the plating solution according to one ormore embodiments of the present invention.

The plating solution according to one or more embodiments of the presentinvention that allows obtaining a plating film of semiglossy appearancewithin this wide current density range elicits the followingadvantageous effects.

Firstly, the obtained tin plating film has excellent homogeneity insurface properties, even in cases where current density exhibits readilyvariability within one batch. Specific examples of such instancesinclude, for instance, cases where multiple members to be plated areplated by barrel plating, or cases where the surface to be plated of themember to be plated is a rugged surface.

Secondly, the obtained tin plating film has excellent homogeneity insurface properties, even in cases where current density exhibits readilyvariability between batches. Specific examples of such instancesinclude, for instance, a case where the shapes and/or total count of themembers to be plated that are fed to barrel plating fluctuate betweenbatches.

(2) Plating Temperature

The plating temperature is not particularly limited. Ordinarily, theplating temperature ranges from 20° C. to 60° C. According to one ormore embodiments of the present invention, the control range of theplating temperature is set to about 5° C., since temperaturefluctuations may result in changes in plating appearance.

(3) Cumulative Current Amount

The cumulative current amount is not particularly limited. If thecumulative current amount is excessively small, a concern arises in thatthe base metal, which comprises nickel or the like, may fail to besufficiently covered and in that solder wettability may fail to beenhanced. On the other hand, an excessively large cumulative currentamount is disadvantageous in economic terms. The range of cumulativecurrent amount is to be appropriately set with the above considerationsin mind.

3. Member Having a Tin Plating Film

A member (hereafter also referred to as “tin plating member”) in which asemiglossy tin plating film is formed on at least part of the surface ofa member to be plated can be produced by performing electroplating in astate where the member to be plated is in contact with the platingsolution according to one or more embodiments of the present invention.

The type of the member to be plated is not particularly limited, so longas at least part of the surface thereof has conductivity. Examples ofsuch members include electronic components. Specific examples ofelectronic components include resistors, variable resistors, capacitors,filters, inductors, thermistors, crystal oscillators, switches,connectors, lead wires, printed circuit boards, and semiconductorintegrated circuits and modules. In a case where the member to be platedis an electronic component, the electronic component may include one,two or more types selected from the group consisting of these electroniccomponents.

The thickness of the plating film on the member to be plated is notparticularly limited, but according to one or more embodiments of thepresent invention, ranges from 1 μm to 5 μm. If the thickness in theplating film is excessively small, there increases the likelihood ofoccurrence of portions at which the plating film fails locally to formproperly. On the other hand, an excessively large thickness of theplating film is not only disadvantageous in economic terms, but resultsalso in an increased likelihood of detachment of the plating film offthe member to be plated.

In the semiglossy tin plating film of the plating member according toone or more embodiments of the present invention, a ratio of 8 or lesscan be achieved for the ratio of glossiness G_(s)(60°) measured inaccordance with JIS 28741: 1997 (ISO 2813: 1994) of the semiglossy tinplating film obtained in a case of electroplating under conditions ofplating temperature of 45° C. and current density of 15 A/dm² withrespect to the ratio of the glossiness G_(s)(60°) of the film obtainedin a case of electroplating under conditions of plating temperature of45° C. and current density of 5 A/dm². If the above ratio is 8 or less,the glossiness G_(s)(60°) of the semiglossy tin plating film in theplating member according to one or more embodiments of the presentinvention is not readily affected by fluctuations in the platingconditions, in particular fluctuations in current density. Accordingly,appearance is highly homogeneous, and quality exhibits likewise highhomogeneity, as described below. According to one or more embodiments ofthe present invention, the ratio is 6 or less, and according to one ormore embodiments of the present invention, 4 or less, and according toone or more embodiments of the present invention, 2 or less.

An overview of the glossiness measurement method according to theabovementioned standard (JIS 28741: 1997 (ISO 2813: 1994)) follows next.

A light beam of a prescribed aperture angle is caused to strike a samplesurface at a prescribed incidence angle. A light beam of prescribedaperture angle that is reflected in the specular reflection direction ismeasured using a photoreceiver.

The incidence optical system is made up of a light source, a firstaperture, a first convex lens disposed between the light source and thefirst aperture, and a second convex lens disposed between the firstaperture and the sample. The first aperture is positioned at the focalpoint of the second convex lens. The first aperture and the first lensmay be omitted in a case where a light source filament is disposed atthe position of the first aperture. The acceptance optical system ismade up of a third convex lens, a second aperture and a photoreceiver,in this order from the sample.

The optical systems are disposed in such a manner that when a mirrorsurface is positioned at the position of the sample, the image at thefirst aperture forms a sharp image at the center of the second aperture.The optical axes of the incidence and acceptance sides intersect at thesample plane.

The incidence angle θ is the angle formed by the normal to the sampleand a line that joins the center of the first aperture and the center ofthe second convex lens (principal point of a lens). The acceptance angleis set to incidence angle θ±0.1° in a case where the incidence angle θis set to 60°±0.2°. The aperture angles of the light source image (angleat which the image of the first aperture spreads at the position of thethird lens) include an angle α₁′ of 0.75°±0.10° in the incidence planeand an angle β₁′ of 2.5°±0.1° in the vertical plane. The aperture anglesof the photoreceiver (angle at which the third lens spreads at theposition of the third lens) include an angle α₂ of 4.4°±0.1° in theincidence plane and an angle β₂ of 11.7°±0.2° in the vertical plane.

A non-polarizing light source is used as the light source. The lightsource and photoreceiver that are ordinarily used correspond to acombination of standard light (standard illuminant) D₆₅ and spectralluminous efficiency V (λ) (color-matching function y (λ) in the XYZcolor system). The readings of the instrument used to measure thereflected light beam must be proportional within a range of 1% of themaximum scale value of the light beam that strikes the photoreceiver.The width of the area of the sample irradiated by the light source, inthe direction perpendicular to the incidence plane, must ordinarily be10 mm or greater.

The mirror-surface glossiness at the prescribed incidence angle 0 at aglass surface having a constant value of refractive index of 1.567, overthe entire visible wavelength range, is taken as a reference value of100% with respect to which other values are expressed. The specularreflectivity ρ₀(60°) is 0.1001 in a case where the incidence angle θ is60°.

The description of the measurement results include the value of themirror-surface glossiness and the device used for measurement.

Observation of the surface of the tin plating member according to one ormore embodiments of the present invention reveals that the grain sizedistribution of plating metal, as observed in surface sections, varieslittle for a current density ranging from 5 A/dm² to 15 A/dm² duringelectroplating. In conventional tin plating solutions, it is observedthat the metal crystal that makes up the plating film formed out of theplating solution tends to become coarser when current density increases.In the plating solution according to one or more embodiments of thepresent invention, however, the crystalline state of the metal thatconstitutes the plating film formed out of the plating solution is notreadily influenced by fluctuations in current density.

In the semiglossy tin plating film of the plating member according toone or more embodiments of the present invention, accordingly,fluctuations of the following parameters relating to peak heights andvalley depths of the roughness-profile do not readily exhibit in-planefluctuation upon measurement of the surface roughness of the surfacemade up of the film.

(i) arithmetical mean roughness Ra in JIS B0601:2001 (correspondingstandard: ISO 4287:1997)

(ii) maximum height Rz in JIS B0601:2001 (corresponding standard:ISO4287:1997)

(iii) maximum height Rz_(JIS) in JIS B0601:2001 (corresponding standard:ISO 4287:1997)

(iv) root mean square roughness Rq in JIS B0601:2001 (correspondingstandard: ISO 4287:1997)

As regards the relationship between current density in the platingprocess time and surface roughness of the semiglossy tin plating film inthe plating member according to one or more embodiments of the presentinvention, the semiglossy tin plating film has a ratio of 1.4 or less ofRa (units: μm) of the semiglossy tin plating film obtained in a case ofelectroplating under conditions of plating temperature of 45° C. andcurrent density of 15 A/dm², with respect to the Ra (units: μm) of thesemiglossy tin plating film obtained in a case of electroplating underconditions of plating temperature of 45° C. and current density of 5A/dm². If the above ratio is 1.4 or less, the surface roughness of thesemiglossy tin plating film in the plating member according to one ormore embodiments of the present invention is not readily affected byfluctuations in the plating conditions, in particular fluctuations incurrent density. Accordingly, appearance is highly homogeneous, andquality exhibits likewise high homogeneity, as described below.According to one or more embodiments of the present invention, the aboveratio is 1.3 or less.

According to one or more embodiments of the present invention, thesemiglossy tin plating film in the plating member has a ratio of 1.5 orless of Rq (units: μm) of the semiglossy tin plating film obtained in acase of electroplating under conditions of plating temperature of 45° C.and current density of 15 A/dm², with respect to the Rq (units: μm) ofthe semiglossy tin plating film obtained in a case of electroplatingunder conditions of plating temperature of 45° C. and current density of5 A/dm². If the above ratio is 1.5 or less, the surface roughness of thesemiglossy tin plating film in the plating member according to one ormore embodiments of the present invention is not readily affected byfluctuations in the plating conditions, in particular fluctuations incurrent density. Accordingly, appearance is highly homogeneous, andquality exhibits likewise high homogeneity, as described below.According to one or more embodiments of the present invention, the aboveratio is 1.3 or less.

According to one or more embodiments of the present invention, thesemiglossy tin plating film in the plating member has a ratio of 1.3 orless of Ry (units: μm) of the semiglossy tin plating film obtained in acase of electroplating under conditions of plating temperature of 45° C.and current density of 15 A/dm², with respect to the Ry (units: μm) ofthe semiglossy tin plating film obtained in a case of electroplatingunder conditions of plating temperature of 45° C. and current density of5 A/dm². If the above ratio is 1.3 or less, the surface roughness of thesemiglossy tin plating film in the plating member according to one ormore embodiments of the present invention is not readily affected byfluctuations in the plating conditions, in particular fluctuations incurrent density. Accordingly, appearance is highly homogeneous, andquality exhibits likewise high homogeneity, as described below.According to one or more embodiments of the present invention, the aboveratio is 1.2 or less, and according to one or more embodiments of thepresent invention, 1.1 or less.

As described above, the glossiness G_(s)(60°) does not vary easily withcurrent density, and hence surface properties, such as solderwettability, are not readily influenced by current density. In the tinplating member according to one or more embodiments of the presentinvention, the ratio (before/after) of zero crossing time (units:seconds) before and after a high-temperature high-humidity environmenttest may be of 2.1 or less for a current density during electroplatingthat ranges from 5 A/dm² to 15 A/dm². The above ratio, according to oneor more embodiments of the present invention, is 1.9 or less, andaccording to one or more embodiments of the present invention, is 1.7 orless, for a current density during electroplating that ranges from 5A/dm² to 15 A/dm². The method of measuring the zero crossing time willbe described below in detail.

In the present disclosure, the zero crossing time denotes the time,after start of the test, at which the force exerted on a test piece by asolder bath becomes 0, i.e., the time, from test start, at which thepulling force on account of wetting of the test piece by solder equalsthe expulsion force exerted by solder on the test piece, as measured ina solderability test according to JIS C60068-2-54: 2009 (IEC60068-2-54:2006), by a balance method.

An overview of the solderability test according to the abovementionedstandard (JIS C60068-2-54: 2009 (IE060068-2-54: 2006)) follows next.

The standard prescribes a test method of solderability of componentterminals having arbitrary shapes. The specimen to be tested issuspended from a high-sensitivity balance (typically a spring system),and is immersed edgewise to a prescribed depth in a bath of moltensolder at a given temperature. The resultant of the vertical forces ofbuoyancy and surface tension acting upon the immersed specimen isdetected and is converted, by a signal converter, to an electric signalwhich is continuously recorded as a function of time on a computer or ahigh-speed chart recorder. The recording may be compared with that of aperfectly wetted specimen of the same nature and dimensions. In thestandard there is tested a stationary mode the purpose whereof is toassess the solderability of a particular site on the specimen.

The size of the solder bath is such that no portion of the specimen isless than 15 mm from the wall, and the depth of the bath is not lessthan 15 mm. The material of the solder bath used in the test should beresistant to molten solder.

The specimen undergoes essentially no pre-treatment, but may be cleanedby immersion in a neutral organic solvent at room temperature.

After mounting the specimen in a suitable holder, the prescribed surfaceportion is immersed in flux at room temperature. The specimen is takenout of the flux, and thereafter excess flux is immediately drained offby standing the specimen vertically on clean filter paper for 1 s to 5s.

The specimen is then suspended vertically 20 mm±5 mm above the surfaceof the solder in the solder bath, which is kept at a prescribedtemperature, for 30 s±15 s, to allow most of the flux solvent toevaporate, and the specimen to dry off, before initiating the test.During drying, the recorder is adjusted to the zero point, andimmediately before the test, oxides are removed from the surface of thesolder using a blade of suitable material.

The terminal of the specimen is then immersed at a speed of 5 mm/s±1mm/s to 20 mm/s±1 mm/s to the specified depth in the molten solder, isheld in this position for a specified time and is then pulled up. Thetime of immersion of the specimen to the prescribed depth may be set to0.2 seconds or less after the specimen starts making contact with themolten solder.

The time sequence of the test is as follows.

1) Flux coating time: 0 seconds, duration: about 5 seconds

2) Excessive flux drain time: about 10 seconds, duration: 1 second to 5seconds

3) Time of specimen suspension on the solder bath: about 15 seconds

4) Preheating time: about 20, seconds, duration 30 seconds±15 seconds

5) Time oxide wiping off the solder surface: about 60 seconds

6) Test start time: about 65 seconds, duration: 1 second to 5 seconds

7) Solder immersion time: up to 70 seconds, duration: 5 seconds

In the above sequence, “time” is the elapsed time from flux coating, and“duration” denotes the duration of the respective procedure.

The following items should be specified. If there is prescribed a testby the balance method for defining a test by a balance method.

a) Degreasing time (if necessary)

b) Ageing method (if necessary)

c) Solder alloy composition

d) Flux type

e) Test temperature

f) Portion to be tested in the specimen

g) Immersion depth

h) Immersion time

i) Immersion rate

j) Parameters to be measured from the recording

k) Acceptable values for these parameters

Embodiments of the present invention are explained next based onexamples, but the present invention is not limited to these examples.

Example 1

(1) Preparation of a Plating Solution

Plating solutions Nos. 1 to 8 were prepared that contained 50 g/L of awater-soluble tin (II)-containing substance in tin content equivalent, 5g/L of a surfactant given in Table 1, 120 ml/L of methanesulfonic acidof 70% methanesulfonic acid (i.e. 84 g/L of methanesulfonic acid) as anelectrolyte component, and water as a solvent. Plating solutions Nos. 7and 8, contained 50 mg/L of benzothiazole was incorporated as abrightening agent. The weight-average molecular weight in Table 1 is avalue for the surfactant.

TABLE 1 Appearance of high- Weight- current average Glossiness G_(s)(60°) density Plating Additive molecular Portion Portion Portion portionsolution component such weight of of 5 of 10 of 15 Glossiness (anomalousNo. as surfactant surfactant A/dm² A/dm² A/dm² ratio deposition) 1 N,N′, N′- 930 78 75 49 1.6 No polyoxyethylene- N-alkyl-(C14- 18)1,3-diaminopropane 2 Polyoxyethylene 1150 178 39 6 30 No polyoxypropylenetallow amine 3 Polyoxyethylene 1350 114 71 7 16 Yes palm oil alkylamine4 Polyoxypropylene 1000 120 19 1 120 No polyoxyethylene alkyl (C8-C18)amine 5 Polyoxyethylene 700 19 0 0 Not Yes (β-naphthyl ether calculable6 Polyoxyethylene 560 194 92 21 9 Yes paracumyl phenyl ether 7Polyoxyalkylene 1300 57 12 6 10 No polycyclic phenyl ether +benzothiazole 8 Polyoxyethylene 560 155 43 15 10 No paracumyl phenylether + benzothiazole (2)Plating process

Electroplating was carried out, under the below-described platingconditions, using the obtained plating solutions 1 to 8.

Plating bath: Hullcell (registered trademark), water tank (byYAMAMOTO-MS Co., Ltd.)

Member to be plated: steel sheet (length 65 mm, width 100 mm, thickness0.2 mm)

Current density: 1 A/dm² to 20 A/dm² (varying depending on the position,with respect to the anode, of the surface to be plated of the member tobe plated)

Plating temperature: 45° C. (control range: ±1° C.)

Cumulative current amount: 5A, 60 seconds

Agitation: Agitation by stirrer tip (750 rpm)

(3) Measurement of Glossiness

Glossiness G_(s)(60°) at an incidence angle of 60° was measured,according to JIS 28741: 1997 (ISO 2813: 1994), in each tin platingmember obtained as a result of the above-described plating process, at aportion at which the current density was 5 A/dm², at a portion at whichthe current density was 10 A/dm², and at a portion at which the currentdensity was 15 A/dm². The device used for measurement was IG-331, byHoriba, Ltd. The measurement results are given in Table 1. Theglossiness G_(s)(60°) of the member to be plated was likewise measured.However, the glossiness G_(s)(60°), which exceeded 200, lay in anon-measurable range.

There was worked out the ratio of the glossiness G_(s)(60°) of theobtained portion for which the current density was 15 A/dm² with respectto the glossiness G_(s)(60°) of the obtained portion for which thecurrent density was 5 A/dm² (glossiness ratio). The results are given inTable 1.

(4) Observation of the High-Current Density Portion

The appearance of the portion at which the current density was 15 A/dm²or higher was observed for each tin plating member that was obtained inaccordance with the above-described plating process. The occurrence ornot of anomarouls deposition was checked. The results are given in Table1.

(5) Observation of the Plating Deposition State

The plating deposition state at the portions corresponding to currentdensity of 5 A/dm², 10 A/dm² and 15 A/dm² was observed using a scanningelectron microscope for each tin plating member obtained in accordancewith the above-described plating process. The results are illustrated inFIGS. 1 to 8. The capture angle in the figures denotes the angle formedby the incidence direction of the electron beam and the normal of theplating film.

(6) Measurement of the Surface Roughness of the Plating Surface

The surface roughness of the surface made up of the plating film, at theportions of current density 5 A/dm², 10 A/dm² and 15 A/dm², wasmeasured, using a surface roughness meter (ultra-deep color 3D shapemeasuring microscope VK-9500, by Keyence Corporation) in the respectivetin plating members obtained in accordance with the above-describedplating process. A ratio of the result at 15 A/dm² with respect to theresult at 5 A/dm² was calculated for each of the following sevenmeasurement items.

Ra: arithmetical mean roughness according to JIS B0601:1994 (whichcorresponds to the arithmetical mean roughness Ra in JIS B0601:2001(corresponding standard: ISO 4287:1997))

Ry: maximum height according to JIS B0601:1994 (which corresponds tomaximum height Rz in JIS B0601:2001 (corresponding standard: ISO4287:1997))

Rz: ten-point height according to JIS B0601:1994 (which corresponds tomaximum height Rz_(JIS) in JIS B0601:2001 (corresponding standard: ISO4287:1997))

RMS: root mean square roughness RMS according to JIS B0601:1994 (whichcorresponds to root mean square roughness Rq in JIS B0601:2001(corresponding standard: ISO 4287:1997))

tp: material ratio for each sampling length of 50% cutoff level,according to JIS B0601:1994 (related to material ratio Rmr (c) over theentire evaluation length in JIS B0601:2001 (corresponding standard: ISO4287:1997))

Sm: mean spacing of profile irregularities according to JIS B0601:1994(which corresponds to the mean width RSm of roughness profile elementsin JIS B0601:2001 (corresponding standard: ISO 4287:1997))

S: mean spacing between local peaks according to JIS B0601:1994

The evaluation results are given Table 2.

TABLE 2 Ra Ry Rz ratio ratio ratio (15 A/ (15 A/ (15 A/ Plating Ra (μm)dm²/ Ry (μm) dm²/ Rz (μm) dm²/ solution 5 10 15 5A/ 5 10 15 5A/ 5 10 155A/ No. A/dm² A/dm² A/dm² dm²) A/dm² A/dm² A/dm² dm²) A/dm² A/dm² A/dm²dm² 1 0.84 0.99 1.09 1.30 9.04  9.29  9.13 1.01 6.67  6.38 7.82 1.17 20.92 1.12 1.49 1.62 9.82 17.21 14.34 1.46 8.09 10.19 11.40 1.41 3 0.870.96 1.49 1.71 7.24  9.00 28.89 3.99 6.02  6.84 13.41 2.23 4 0.67 0.831.29 1.93 4.84  9.34 12.02 2.48 4.14  5.87  9.14 2.21 5 1.18 1.61 1.811.53 11.15  13.39 15.65 1.40 8.41 10.46 14.56 1.73 6 0.79 0.95 1.49 1.899.01  9.00 23.28 2.58 6.34  6.40 12.15 1.92 7 0.90 1.38 1.64 1.82 5.9521.61 20.62 3.47 5.47 13.59 13.88 2.54 8 0.92 1.24 1.48 1.61 9.58 12.1616.93 1.77 6.78  8.40 12.81 1.89 RMS ratio tp ratio Plating RMS (μm) (15A/ tp (%) (15 A/dm²/ solution 5 10 15 dm²/5 5 10 15 5 No. A/dm² A/dm²A/dm² A/dm²) A/dm² A/dm² A/dm² A/dm²) 1 1.13 1.22 1.42 1.26 19.14 28.9151.86 2.71 2 1.27 1.58 2.11 1.66 23.93  1.86 92.82 3.88 3 1.11 1.26 2.852.57 22.41 74.71 58.50 2.61 4 0.85 1.06 1.66 1.95 33.74 37.26 54.15 1.605 1.54 2.02 2.41 1.56 58.11 32.42 88.59 1.52 6 1.05 1.22 2.28 2.17 58.3070.95 86.38 1.48 7 1.10 2.06 2.20 2.00 39.55 76.56 95.31 2.41 8 1.191.60 2.07 1.74 39.40 86.67 90.92 2.31 Sm ratio S ratio Plating Sm (μm)(15 A/dm²/ S (mm) (15 A/dm²/ solution 5 10 15 5 5 10 15 5 No. A/dm²A/dm² A/dm² A/dm² A/dm² A/dm² A/dm² A/dm²) 1 13.54 14.92 17.90 1.32 5.987.05 5.93 0.99 2 15.13 14.67 17.93 1.19 5.88 5.16 4.81 0.82 3 13.9816.48 16.13 1.15 5.27 5.43 5.49 1.04 4 12.87 14.86 16.36 1.27 5.74 4.804.54 0.79 5 14.57 17.53 16.45 1.13 4.75 4.49 4.37 0.92 6 12.61 16.6316.89 1.34 5.93 5.63 5.59 0.94 7 13.78 16.51 16.63 1.21 5.51 5.63 5.851.06 8 13.77 16.05 15.32 1.11 4.74 5.74 5.87 1.24

Example 2 (1) Plating Process

Plating was carried out under the below-described plating conditionsusing the plating solutions 1, 2, 5 and 6 prepared in Example 1. Thesubstrate to be plated was an open-frame printed board, in whichelectrolytic nickel plating (sulfamic acid bath, 1 μm) was formed onwiring comprising C1020, and which was then cleaned and activated inaccordance with known methods, to yield test pieces for evaluation ofzero crossing time. The average thickness of the tin plating film in thetest pieces was 3 μm.

Current density: 5 A/dm², 10 A/dm² or 15 A/dm²

Plating temperature: 45° C. (control range: ±1° C.)

Cumulative current amount: 300 A·sec/dm²

Other plating conditions: stirred plating (stirrer revolutions 500 rpm),with rocking, (cathode rocker, 5 m/minute)

(2) Measurement of Zero Crossing Time (Before Environment Test)

A solderability test by the balance method according to JIS C60068-2-54:2009 (IEC60068-2-54: 2006) was carried out using each of the pluralityof test pieces for zero crossing time measurement of dissimilar platingsolutions and/or current densities, obtained in accordance with theabove-described plating process. Specifically, the surface of the testpieces was cleaned and the test pieces were immersed for 2 seconds inthe below-described flux. Thereafter, the test pieces were taken out ofthe flux, and the drooping residual solution on the surface of the testpieces was removed. The test pieces, with the oxide film on the surfacethereof removed, were quickly immersed, after droop-removal, in thesolder bath, to carry out the test thereby. After start of the immersionof the test pieces in the solder bath, the zero crossing time was workedout as the time that it took for the force of the solder bath acting onthe test pieces to reach 0 (time elapsed from test start until wettingbegins). The zero crossing time is substantially identical to the testtime that it takes a recorded signal trace to intersect a zero balancepoint in a device for measuring a wetting curve, as prescribed in MILSTD-883 METHOD 2022. The test conditions and so forth were as follows.

Used device: SAT-5100, by RHESCA Corporation

Solder: M7005, by Senju Metal Industry Co., Ltd.

Solder composition: Sn-3.0 wt %, Ag-0.5 wt %, balance Cu

Solder temperature: 245° C.±5° C.

Flux: ES-1061, by Senju Metal Industry Co., Ltd.

Immersion speed of test piece: 2 mm/second

Immersion depth of test piece: 1 mm

Immersion time of test piece: 5 seconds

The measurement results for the zero crossing time of each test pieceare given in Table 3.

(3) Measurement of Zero Crossing Time (after Environment Test)

The plurality of types of test pieces for zero crossing time measurementobtained in accordance with the above-described plating process werekept in a high-temperature high-humidity environment, at 105° C. and ata relative humidity of 100%, for 8 hours. After the environment test,the zero crossing time of the test pieces was measured as describedabove. The measurement results for the zero crossing time of each testpiece are given in Table 2. The ratio of the zero crossing time beforeand after the environment test was worked out for each test piece out onthe basis of the respective measurement results (after test/beforetest). The results are given in Table 3.

TABLE 3 Ratio (before/after) of Zero crossing Zero crossing zerocrossing time time (sec) before time (sec) after before and afterPlating environment test environment test environment test solution 5 1015 5 10 15 5 10 15 No. A/dm² A/dm² A/dm² A/dm² A/dm² A/dm² A/dm² A/dm²A/dm² 1 0.28 0.30 0.30 0.49 0.51 0.47 1.7 1.7 1.6 2 0.28 0.29 0.27 0.480.50 0.65 1.7 1.7 2.4 5 0.29 0.30 0.28 0.67 0.68 0.70 2.3 2.3 2.5 6 0.300.28 0.30 0.64 0.57 0.47 2.2 2.0 1.6

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

What is claimed is:
 1. An acidic aqueous composition for semiglossy tinelectroplating, comprising: a water-soluble tin (II)-containingsubstance; and a surfactant, wherein said surfactant comprises asurfactant (A) comprisingN,N′,N′-polyoxyethylene-N-alkyl-1,3-diaminopropane.
 2. The acidicaqueous composition for semiglossy tin electroplating according to claim1, wherein, in said surfactant (A), the number of carbon atoms of thealkyl group that bonds to N ranges from 14 to
 18. 3. The acidic aqueouscomposition for semiglossy tin electroplating according to claim 1,wherein the weight-average molecular weight of said surfactant (A)ranges from 300 to
 1500. 4. The acidic aqueous composition forsemiglossy tin electroplating according to claim 1, wherein the contentof said water-soluble tin (II)-containing substance in tin contentequivalent ranges from 5 g/L to 200 g/L and the content of saidsurfactant (A) ranges from 0.5 g/L to 40 g/L.
 5. The acidic aqueouscomposition for semiglossy tin electroplating according to claim 1,which contains an organic sulfonic acid compound.
 6. The acidic aqueouscomposition for semiglossy tin electroplating according to claim 5,wherein the content of said organic sulfonic acid compound ranges from50 g/L to 300 g/L in organic sulfonic acid content equivalent.
 7. Amember, comprising: a member to be plated; and a semiglossy tin platingfilm that is formed on at least part of the surface of said member to beplated, by electroplating of acidic aqueous composition for semiglossytin electroplating comprising: a water-soluble tin (II)-containingsubstance; and a surfactant, wherein said surfactant comprises asurfactant (A) comprisingN,N′,N′-polyoxyethylene-N-alkyl-1,3-diaminopropane.
 8. The memberaccording to claim 7, wherein said semiglossy tin plating film in saidmember is electroplated under a condition of current density of 5 A/dm²or higher.
 9. The member according to claim 7, wherein said semiglossytin plating film of said member has a ratio of 8 or less of glossinessGs(60°) measured in accordance with JIS 28741: 1997 (ISO 2813: 1994) ofthe semiglossy tin plating film obtained in a case of electroplatingunder conditions of plating temperature of 45° C. and current density of15 A/dm², with respect to said glossiness Gs(60°) of the semiglossy tinplating film obtained in a case of electroplating under conditions ofplating temperature of 45° C. and current density of 5 A/dm².
 10. Themember according to claim 7, wherein said semiglossy tin plating film insaid plating member has a ratio of 1.3 or less of arithmetical meanroughness Ra measured according to JIS B0601:2001 (ISO 4287:1997) of thesemiglossy tin plating film obtained in a case of electroplating underconditions of plating temperature of 45° C. and current density of 15A/dm², with respect to said arithmetical mean roughness Ra of thesemiglossy tin plating film obtained in a case of electroplating underconditions of plating temperature of 45° C. and current density of 5A/dm².
 11. The member according to claim 7, wherein said semiglossy tinplating film in said plating member has a ratio of 1.3 or less of rootmean square roughness Rq measured according to JIS B0601:2001 (ISO4287:1997) of the semiglossy tin plating film obtained in a case ofelectroplating under conditions of plating temperature of 45° C. andcurrent density of 15 A/dm², with respect to said root mean squareroughness Rq of the semiglossy tin plating film obtained in a case ofelectroplating under conditions of plating temperature of 45° C. andcurrent density of 5 A/dm².
 12. The member according to claim 7, whereinsaid semiglossy tin plating film in said member has a thickness rangingfrom 1 μm to 5 μm.
 13. The member according to claim 7, wherein saidsemiglossy tin plating film in said member is formed by electroplatingwith a current density ranging from 5 A/dm² to 15 A/dm², and a ratio(before/after) of a value (unit: seconds) of zero crossing time (unit:seconds) of said member as measured in a solderability test by a balancemethod according to JIS C60068-2-54: 2009 (IEC60068-2-54: 2006) after anenvironment test of standing for 8 hours in an environment at 105° C.and relative humidity of 100%, with respect to the value (unit: seconds)measured before the environment test, is 2.1 or less.
 14. The memberaccording to claim 7, wherein said member to be plated is an electroniccomponent.
 15. The member according to claim 14, wherein said electroniccomponent includes one, two or more types selected from the groupconsisting of resistors, variable resistors, capacitors, filters,inductors, thermistors, crystal oscillators, switches, connectors, leadwires, printed circuit boards, and semiconductor integrated circuits andmodules.
 16. The member according to claim 7, wherein, in saidsurfactant (A), the number of carbon atoms of the alkyl group that bondsto N ranges from 14 to
 18. 17. The member according to claim 7, whereinthe weight-average molecular weight of said surfactant (A) ranges from300 to
 1500. 18. The member according to claim 7, wherein the content ofsaid water-soluble tin (II)-containing substance in tin contentequivalent ranges from 5 g/L to 200 g/L and the content of saidsurfactant (A) ranges from 0.5 g/L to 40 g/L.
 19. The member accordingto claim 7, which contains an organic sulfonic acid compound.
 20. Themember according to claim 19, wherein the content of said organicsulfonic acid compound ranges from 50 g/L to 300 g/L in organic sulfonicacid content equivalent.